After 5 years and 120k+ miles on my 1-ton 2nd Gen Dually since brand new, my six Yokohama TY303 tires are ready for regrooving.

However, I have not yet been able to find out the maximum, recommended limit that can be re-grooved from the top of the wear-bar-indicator now showing in the bottom of the tire tread patterns.

Obviously, I don't want to cut into any of the steel bands, so if anyone has suggestions, knowledge and/or experience of what the maximum depth in millimeters should be set to cut and re-groove these tread patterns, I'd be very grateful!

Cheers!!